Nuclear: A nuclear weapon[a] is an

A nuclear weapon[a] is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission (fission or atomic bomb) or a combination of fission and nuclear fusion reactions (thermonuclear weapon [b]), producing a nuclear explosion. Both bomb types release large quantities of energy from relatively small amounts of matter. Nuclear weapons have had yields between 10 tons (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). Yields in the low ... Nuclear fusion is the process by which two light atomic nuclei combine to form a single heavier one while releasing massive amounts of energy. Fusion reactions take place in a state of matter called plasma — a hot, charged gas made of positive ions and free-moving electrons with unique properties distinct from solids, liquids or gases. Nuclear power plants must be protected since the material inside a nuclear power plant can be used by terrorists. Nuclear power plants have armed guards, many different kinds of fences and barriers, cameras and many controls on who can come into the plant. The first commercial nuclear power stations started operation in the 1950s. Nuclear energy now provides about 9% of the world's electricity from about 440 power reactors. 31 countries generate electricity from nuclear energy. Nuclear provides about one-quarter of the world’s low-carbon electricity.